Energy Storage

Energy Storage
• Energy storage systems are the set of methods and technologies used to store
various forms of energy.
• Energy storage devices can be categorized as mechanical, electrochemical,
chemical, electrical, or thermal devices, depending on the storage technology .
• The performance of energy storage devices can be defined by their output and
energy density.
• Energy storage systems have traditionally been very expensive and not
economically viable on a commercial scale. However, drastic improvements in
energy storage technologies have led to decreases in costs and improved
technology applications.
 Why Energy Storage
• The following high-level summary identifies the main future uses and applications of
large-scale energy storage technologies:
Time shifting: time shifting refers to the use of grid electricity to charge an energy
storage system when supply exceeds demand or when electricity is cheap, and the use of
such stored energy in peak demand periods.
Peak shaving: peak shaving refers to the use of electrical energy stored during off-peak
periods, to compensate generation deficits during periods peak demand periods.
Load levelling: load levelling is a supply-side support measure designed to level or
follow changing load patterns in real time.
Low-voltage ride-through: low-voltage ride through is the capability to mitigate low
voltage periods when these occur, and is a voltage control measure necessary when
external voltage fluctuations occur.
ESS
• Transmission and distribution stabilisation: energy storage systems can be used to
support the synchronous operation of components on a power transmission line, or to
regulate the power quality in the distribution grid.
Black-start: energy storage systems can provide the capability to start up generation
operations, for example from a shutdown condition, without having to take supplies from
the grid
Voltage regulation and control: electric power systems react dynamically to changes in
active and reactive power, thus influencing the magnitude and profile of the voltage in
networks.
Suppression of network fluctuations: while power fluctuations occur permanently on
the electricity grid, their existence threatens modern power electronics components and
must therefore be minimised.
ESS
• Spinning reserve: in situations where there is a rapid decrease of the load, or a
fast increase
of additional on-line generation facilities, energy storage systems can assume the
role and function of a spinning reserve, provided such systems can respond
rapidly, and maintaining outputs until the situations can be brought under control
using more conventional load control measures
• Standing reserve: standing reserves are used to deal with network constraints
arising when the electricity demand exceeds the supply, which can happen when
load forecasts are inaccurate, or in case unexpected plant outage occurs
Emergency back-up power and uninterruptible power supply: in case of a
power failure, energy storage units have traditionally been used to provide
emergency back-up power services, including those needed to ensure the short-
term provision of uninterruptible power supply (UPS).
 CONTEMPORARY ENERGY STORAGE SYSTEMS

1. Mechanical systems: pumped hydroelectric storage, compressed air storage,

flywheels, and similar systems.
2. Electro-chemical systems: Lead-acid batteries, lithium-ion batteries, sodium-
Sulphur batteries and flow batteries.
3. Electrical systems: Super capacitors and superconducting magnetic systems;
4. Thermal systems: Heat storage systems.
5. Thermo-chemical and chemical systems: Hydrogen and other fuels.
Battery Energy Storage System
• A battery is a device that produces
electrical energy from chemical
reactions. There are different kinds
of batteries with different
chemicals.
Battery technology
Lead Acid Battery
Lithium-Ion (Li-Ion) Battery
Redox Flow Battery (RFB)
Nickel–Cadmium (Ni–Cd) Nickel–Metal Hydride (Ni–MH)
Battery Battery
BESS
 Super Capacitor
• The supercapacitor, also known as ultracapacitor or double-layer capacitor, differs from a regular capacitor in
that it has very high capacitance. A capacitor stores energy by means of a static charge as opposed to an
electrochemical reaction. Applying a voltage differential on the positive and negative plates charges the
capacitor. This is similar to the buildup of electrical charge when walking on a carpet.

• There are three types of capacitors and the most basic is the electrostatic capacitor with a dry separator. This
classic capacitor has very low capacitance and is mainly used to tune radio frequencies and filtering. The size
ranges from a few pico-farads (pf) to low microfarad (μF).
• The electrolytic capacitor provides higher capacitance than the electrostatic capacitor and is rated in
microfarads (μF), which is a million times larger than a pico-farad. These capacitors deploy a moist separator
and are used for filtering, buffering and signal coupling. Similar to a battery, the electrostatic capacity has a
positive and negative that must be observed.

The third type is the supercapacitor, rated in farads, which is thousands of times higher than the electrolytic
capacitor. The supercapacitor is used for energy storage undergoing frequent charge and discharge cycles at
high current and short duration.
Supercapacitor
FUEL CELL
What is a fuel cell?
• A fuel cell is like a battery in that it generates electricity from an electrochemical reaction. Both batteries and
fuel cells convert chemical energy into electrical energy and also, as a by-product of this process, into heat.
However, a battery holds a closed store of energy within it and once this is depleted the battery must be
discarded, or recharged by using an external supply of electricity to drive the electrochemical reaction in the
reverse direction.
• All fuel cells are based around a central design using two electrodes separated by a solid or
liquid electrolyte that carries electrically charged particles between them. A catalyst is often used to speed up
the reactions at the electrodes. Fuel cell types are generally classified according to the nature of the electrolyte
they use. Each type requires particular materials and fuels and is suitable for different applications.
• A fuel cell, on the other hand, uses an external supply of chemical energy and can run indefinitely, as long as
it is supplied with a source of hydrogen and a source of oxygen (usually air). The source of hydrogen is
generally referred to as the fuel and this gives the fuel cell its name, although there is no combustion involved.
Oxidation of the hydrogen instead takes place electrochemically in a very efficient way. During oxidation,
hydrogen atoms react with oxygen atoms to form water; in the process electrons are released and flow through
an external circuit as an electric current.
Types Of Fuel Cell
Types Of Fuel Cell
Types Of Fuel Cell
Pumped Storage Hydroelectricity (PSH)

• It is considered to be the only possible way to store energy in a huge amount

while maintaining a high efficiency and being economical as well in today’s grid
• When you lift an object of a certain mass you overcome gravity. In order to do so
you must supply a force over a height. The force required to lift is defined by the
physical law (m for mass and a for acceleration), but in this case a is replaced by
for the gravitational acceleration (9.81 meters per square second [m/s2]). The
work, meaning the energy supplied and therefore stored in the object is defined
by (in this example the term for distance can be replaced by for height). This
results in W , meaning the energy stored equals the mass multiplied by the gravity
and the height.
• In times of low electricity demand and high production, water is pumped from the
lower reservoir into the higher, storing the electricity in the water in
the form of potential energy. When needed, for example on peak demand, the
water can be released, flowing down the pipes again and back through the
turbine which then generates the electricity.
• The general formula for the power output is P=Q ×H × g × ρ × η , including the
factors of volume flow rate passing the turbines (Q ), the hydraulic efficiency of
the
turbine (η) and the density of the water (ρ),Earth Gravity (g),Reservoir Head(H) .
 Underground Pumped-Storage
Hydroelectricity
Pumped Storage

• Pros
Mature technology, capable of storing
huge amounts of energy
High overall efficiency (around 70-80
percent)
Fast response times
Inexpensive way to store energy
• Cons Few potential sites
Huge environmental impacts
Requires a significant huge water source.
 Flywheel
• Flywheel is a disk with a certain amount of mass that spins, holding
kinetic energy.
• Modern high-tech flywheels are built with the disk attached to a rotor in
upright position to prevent gravity influence. They are charged by a
simple electric motor that simultaneously acts as a generator in the
process of discharging .
• The challenge to increase that efficiency is to minimize friction. This is
mainly accomplished by two measures: the first one is to let the disk spin
in a vacuum, so there will be no air friction; and the second one is to bear
the spinning rotor on permanent and electromagnetic bearings so it
basically floats.
• Pros
Low maintenance and long lifespan: up to 20 years
Almost no carbon emissions
Fast response times
No toxic components.
• Cons
High acquisition costs
Low storage capacity
High self-discharge (3 –20 percent per hour)
 Superconducting Magnetic Energy Storage (SMES)
• The system consists of three major components: the coil, the power conditioning system (PCS) and a
cooling system.
• The idea is to store energy in the form of an electromagnetic field surrounding the coil, which is made of
a superconductor. (niobium-titanium -264º C [9º K], niobium-tin 255ºC [18 K]).
• This can be accomplished by liquefying helium; but, it is very expensive and the process lowers the
efficiency .
• The PCS is the interface between the SMES coil and the power system. Its task is to convert alternating
current (AC) into direct current (DC) and vice versa since the coil is only capable of storing and releasing
the energy in the form of DC.
• Pros
Fast respond times
Capable of partial and deep discharges
• No environmental hazard.
• Cons:
High energy losses (~12 percent per day)
Very expensive in production and maintenance
Reduced efficiency due to the required cooling process.
 Compressed Air Energy Storage (CAES)

• The basic idea is to use an electric compressor to compress air to a pressure of about 60 bars and store it in giant
underground spaces like old salt caverns, aquifers or pore storage sites and to power a turbine to generate electricity
again when demanded. These cavern storages are sealed airtight as proved by the existing two plants and have also been
used to store natural gas for years now.

• Two major problems when it comes to pressuring air. First, compressing the air leads to a very significant amount of heat
generation and subsequent power loss the air will freeze the power turbine when decompressed .

• Instead of using the combustion of the gas to compress the air like in a conventional gas turbine, the stored air in the
caverns can be used, meaning that, technically, these CAES plants both store and produce electricity .

• Pros and
Capable of storing huge amounts of energy, similar to PSH
AA-CAES capable of efficiencies nearly as good as PSH (around 70 percent)
Fast response times
Inexpensive way to store energy.

• Cons
Requires sealed storage caverns
Economical only up to a day of storage (for AA-CAES)
Competing against other storage needs (natural gas, hydrogen)
Not yet fully developed
Electrolysis of water and Methanation

• Another Idea would be to use the

excess electricity of renewable energies
to make hydrogen (H2) through
electrolysis of water and, in further
steps, methane. Both methane and
hydrogen could be stored in existing
natural gas grids
Thermal Storage
• Thermal storage is the concept of
storing energy in form of heat.
• one of the most promising is the
concept of phase changing
materials (PCM).
• As solar thermal power plants use
the heat of the sun during the day
to simultaneously produce
electricity and “fill up” the
thermal storage tanks, which
allows them to generate electricity
at night.
Thank You